GB760030A - Process for the manufacture of dispersive, water-soluble alginates with high solubility speed - Google Patents

Abstract

Water-soluble alginates are obtained in a dispersive form more readily soluble in water by subjecting a paste of the alginate having a water-content of 50-90 per cent by weight to kneading and extrusion under mechanical pressure in a pressing device, grinding the pressed product in a rotary crushing apparatus, the peripheral speed of the revolving grinding members of which is greater than 10 m./sec. and drying the ground product. The pressing device may be a closed cylinder, in which the alginate paste is placed, provided therein with an oscillating perforated pestle, the paste being driven through the perforations of the moving pestle; alternatively an unperforated pestle may be used, the cylinder then being provided with perforated sheets or the like. The preferred pressing devices, for continuous operation, are worm presses or kneading pumps, e.g. a meat mincer, and the paste issuing from the orifice of the appliance may be in the form of ropes, ribbons, strips or the like. The grinding apparatus may be a hammer basket mill, the hammers of which have sharp cutting edges and/or are surrounded by a basket of perforated metal sheet, or a crushing device comprising at least one pair of plates, spaced a short distance apart and capable of relative movement, each plate being provided on one face with teeth or other projections. Drying of the ground product may be effected on belt, drum or plate driers, preferably at below 120 DEG C. The process may be applied to the treatment of sodium, potassium, ammonium, magnesium and organic base salts of alginic acid including the trimethylamine, triethanolamine and tetramethyl ammonium hydroxide salts. Examples are given, in one of which sodium alginate is prepared by kneading anhydrous sodium carbonate into a paste of alginic acid in a kneading pump.